1. Field of The Invention
The present invention relates to a spring-incorporated flat type terminal structure which is used in a limited space, e.g., in an electric vehicle, and is suitable for connection of electrical wires, which have a large current capacity.
2. Description Of The Prior Art
A variety of connecting terminals for wires having a large current capacity, such as used in electric vehicles, have been proposed. A first example of conventional connecting connectors is a round type machined terminal 1, as shown in FIG. 8. The machined terminal comprises a cylindrical terminal engaging section 2 and a wire connecting section 3, which is coaxial with the cylindrical terminal engaging section 2 and is connected to a large current wire W (FIG. 9).
As shown in FIG. 9, which is a sectional view taken along line D--D of FIG. 8, the terminal engaging section 2 includes a hollow cylindrical portion, the inside diameter of which is larger than the diameter of the opening of a terminal inserting hole 2a. A cylindrical spring 4, which is flexible, is accommodated in the hollow cylindrical portion 2b. When a male terminal having a circular cross section is inserted into the machined terminal, the cylindrical spring 4 is compressed radially, so that the male terminal is electrically connected through the cylindrical spring 4 to the inner cylindrical surface of the hollow cylindrical portion 2b.
As shown in FIG. 10, the cylindrical spring 4 has a plurality of protrusions 4c at both ends to lock itself in the hollow cylindrical portion 2b and to guide the male terminal into the terminal 1. A plurality of slits 4b are cut in the body of the cylindrical spring to form contact portions 4a between the slits 4b. The contact portions 4a are bent inwardly to contact the male terminal when the latter is inserted into the terminal 1.
A second example of a conventional connecting terminal is a round type machined terminal disclosed by Japanese Patent Application (OPI) No. 124383/1988 (the term "OPI" as used herein means an "unexamined application"). In the round type machined terminal of the latter OPI, a sleeve on the inner wall surface, on which a flat-plate-shaped spring is mounted, is fitted in a cylindrical supporting member corresponding to the terminal engaging section, thus forming a terminal engaging section similar to the one in the above-described first example.
Connecting terminals in an electric vehicle use heavy wires to handle large currents. Hence, in disengaging the connecting terminals, it is considerably difficult to retract or bend them, even in the case of a single connecting terminal. It is even more difficult in a narrow vehicle to obtain the requisite space, which is large enough to bend the terminal.
A connecting terminal for handling large currents should have a large enough electrical contact surface to suppress the generation of heat; however, round type machined terminals do not have such large contact surfaces.
Additionally, in the connecting terminal of the above first example, in order to lock the spring, it is necessary to form undercuts in the inner cylindrical surface of the hollow cylindrical portion. On the other hand, the connecting terminal of the second example requires a sleeve to fixedly accommodate the spring, and this increases the number of components and, accordingly, the manufacturing cost of the connecting terminal.